It is well known that the power and power density of semiconductor chips are increasing rapidly.
Because of this high power and power density, a great portion of the resistance of the heat flow is from the chip to the heat sinking device which usually has much larger size than the chip does. A better heat transfer device that can mitigate this thermal resistance and provide better heat transfer from a tiny chip to a heat sinking device is therefore desired.
U.S. Pat. No. 4,519,447-“Substrate Cooling” teaches two methods for cooling a substrate, one is a flat vapor chamber for heat spreading and the other is a magnetohydrodynamically driven liquid cooling plate.
U.S. Pat. No. 5,316,077-“Heat Sink for Electrical Circuit Components” teaches a method to form a coolant passages by means of two plates. A pump is used to drive the liquid coolant moving through the passages and carry the heat from the components to the fins on one plate. An expansion chamber is used to accommodate the expansion of the liquid coolant.
U.S. Pat. No. 6,019,165-“Heat Exchange Apparatus” teaches a method of using a centripetal pump impeller driven by an external magnetic field to move liquid coolant inside a thermal spreader plate and transfer heat from heat sources to heat absorber which is in good thermal contact with the thermal plate directly.
U.S. Pat. No. 6,029,742-“Heat Exchanger for Electronic Equipment” teaches a method using a magnetic coupled centrifugal rotor assembly in a pipe to drive the coolant within the pipe for removing heat from an electronic equipment.